Photographic fixing procedure and baths



Patented Dec. 17, 1946 PHG'EOGRAPHIC I FIXING. PROCEDURE AND BATHS JohnI; Crabtreeand George. T. Eaton, Bochesten. N. Y., assignorsto EastmanKodak Company, Bpchester, N. Y., a corporation of New Jersey No Drawing.Application September 117,, 1943,, Serial No. 502,790.

8'Claims. 1

This invention relates to improved photographic procedure for thetreatment of non-gelatin emulsion photographic elements and inparticular to improved procedure for fixing. such photographic elements.The invention also pertains to improved fixing compositions for suchphotographic elements.

. Various non-gelatin materials have been used heretofore as protectivecolloids or carriers as a substitute for gelatin in, photographic silverhalide emulsions. Thus, resins such as cellulose nitrate, acetate,acetate-butyrate; polyvinyl acetals such as polyvinyl acetaldehydeacetal and polyvinyl butyraldehyde acetal; cold water soluble polyvinylacetaldehyde acetal, polyvinyl alcohol and polyvinyl esters such ashydrolyzed polyvinyl acetate have been used for this purpose. Thesesubstitutes are superior to gelatin in many respects but it has beennoted that they frequently are not satisfactorily permeated by fixingsolutions so that the removal of silver halide by conventional fixingsolutions has in many cases been incomplete or required an inordinatelylong period of time.

This invention has for its object to provide improved procedure for thefixing of photographic elements bearing a non-gelatin emulsion. Anotherobject is to provide improved fixing compositions which permit rapidfixing of non-gelatin emulsions, and especially those which have limitedpermeability to water or to the usual fixing baths. Other objects are toimprove the state of the art.

These and other objects are accomplished by our invention which includesimmersing a photographic element, which comprises a non-gelatin layercontaining a developed silver halide photographic image, in a bath whichcontains a simple salt of hydrogen iodide such as an alkali metal orammonium iodide and a member of the group consisting of thiourea andthiocyanate as the essential fixing constituents.

In the following examples and description we have given several of thepreferred embodiments of our invention, but it is to be understood thatthese are set forth for the purpose of illustration and not inlimitation thereof.

Examples of suitable iodides are sodium and potassium and ammoniumiodide. Examples of thiocyanates which may be used are sodium, potassiumand ammonium thiocyanate; organic thiocyanates such as thiocyanocatecholmay be used, but we prefer to use inorganic thiocyanates.

The iodide-thiourea mixtures are preferably used in aqueous solutionscontaining between in three to three and one-half minutes.

about 8% and v 25% iodide to betweenabout .25, and 8% thiourea- The.amount. of. iodi'dain the iodide-thiocyanate mixture is. somewhat morethe other fixing agent. Fixing baths containing. the above-noted.proportions of the. essential, fix,-, ing constituents have, beentested, and in each. case have been found to give a, fixing time1offithree, to three and. one-half minutes or. less. The exact proportionsand quantities used depend upon the composition of the non-gelatincarriers which have been produced with sufiicient vari ation instructure to require fixing baths embodying all of the proportions givenabove. Proportions somewhat outside the ranges or amounts given can beused with satisfactory results if slower fixing times can be tolerated.In general the higher the concentration of both of the constituents theshorter will be the fixing time. Proportions in the higher ranges arenot ordinarily used except for non-gelatin emulsions which are veryimpermeable. The concentrations indicated give a completely clear filmfree of silver halide Similar tests with a conventional fixing bathcontaining 30% hypo required an hour for a similar degree of fixing.

The invention is applicable to non-gelatin emulsions in general and willenable shorter fixing times with all such emulsions. It is of particularvalue in connection with those non-gelatin emulsions which have limitedpermeability to water.

What we claim is:

1. The process of permeating and fixing a photographic element whichincludes a nongelatin layer having slight permeability to normal fixingsolutions and containing a developed silver image which processcomprises immersing said photographic element in a bath which containsas the essential fixing constituents from 8% to 25% of a water solublesimple salt of hydrogen iodide and a member of the group consisting ofthiourea in the amount of 0.25 %-87% and a soluble thiocyanate in theamount of 5%-25%, in the latter case the amount of iodide being about25%.

2. The process of permeating and fixing a photographic element whichincludes a nongelatin layer having slight permeability to normal fixingsolutions and containing a developed and 25% thiocyanate.

3 silver image which process comprises immersing said photographicelement in a bath which contains as the essential fixing constituentsbetween about 8% and 25% alkali metal iodide and between about 0.25% and8% thiourea.

3. The process of permeating and fixing a photographic element whichincludes a nongelatin layer having slight permeability to normal fixingsolutions and containing a developed silver image, which processcomprises immersing said photographic element in a bath which containsas the essential fixing constituent between about 8% and 25% potassiumiodide and between about 0.25% and 8% thiourea.

4. The process of permeating and fixing a photographic element whichincludes a nongelatin layer having slight permeability to normal fixingsolutions and containing a developed silver image which processcomprises immersing said photographic element in a bath which containsas the essential fixing constituents about 25% alkali metal iodide andbetween about and 25% thiocyanate.

5. The process of permeating and fixing a photographic element whichincludes a nongelatin layer having slight permeability to normal fixingsolutions and containing a developed silver image, which processcomprises immersing said photographic element in a bath which containsas the essential fixing constituents about 25% potassium iodide andbetween about 5% and 25% thiocyanate.

6. The process of permeating and fixing a photographic element whichincludes a nongelatin layer containing a developed silver image andrequiring approximately one hour for penetration by a normal fixingsolution which process comprises immersing said photographic element ina bath which contains as the essential fixing constituents from 8% to25% of potassium iodide and a member of the group consisting of thioureain the amount of 0.25%-8% and a soluble thiocyanate in the amount of5%-25%, in the latter case the amount of iodide being about 25%.

7. The process of permeating and fixing a photographic element whichincludes a nongelatin layer containing a developed silver image andrequiring approximately one hour for penetration by a normal fixingsolution which process comprises immersing said photographic element ina bath which contains as the essential fixing constituents between about8% and 25% potassium iodide and between about 0.25% and 8% thiourea.

8. The process of permeating and fixing a photographic element whichincludes a nongelatin layer containing a developed silver image andrequiring approximately one hour for penetration by a normal fixingsolution which process comprises immersing said photographic element ina bath which contains as the essential fixing constituents about 25%potassium iodide and between about 5% and 25% thiocyanate.

J. I. CRABTREE. GEORGE T. EATON.

